1. Field of the Invention
The present invention relates to a computer numerical control (CNC) servo drive system and, more particularly, to a system capable of simultaneously driving multiple servo motors through a controller and a driver.
2. Description of the Related Art
Servo motors of CNC servo drive systems can perform accurate control over location and motion thereof, such as rotation speed, fast switch of forward and reverse rotation, accurate positioning and the like, and are oftentimes applied to automation of numerically controlled processes in car industry or for metal working machines. The working concepts of the CNC servo drive system reside in that users input a command to a controller, and after compilation of the command, control information is transmitted to a driver for the driver to drive a servo motor to perform motion, such as moving a tool, cutting or milling a workpiece with a tool, and the like, according to the control information.
With reference to FIG. 6, a conventional CNC servo drive system 90 includes a control box 91 and machining equipment 92. The control box 91 is normally a controller 911 in connection with three drivers 912 for the purpose of providing driving signals. The machining equipment 92 includes three servo motors 921 respectively responsible for machining processes in X axis, Y axis and Z axis. When each driver 912 is connected to one of the servo motors 921, the operating time of the servo motor 921 at a highest rotation speed is quite short. The servo motor 921 is only operated with a maximum current upon start, instantaneous acceleration and instantaneous stop of the servo motor 921, and the operation time for the servo motor 921 to maintain at those operation states is not a long period but in merely approximately 1 to 3 seconds. During the rest of operation, the rotation speed of the servo motor 921 is normally low (rated rotation speed) so that the load current of the servo motor 921 is relatively small with a current value being 30% of current required by the drivers 912 regularly and 10% for a lowest current condition. As can be seen from the operation of the servo motor 921, a significant amount of current is not effectively utilized. In case of mass production, not only may human errors arise from the necessity of inputting control commands to each control box 91, but the equipment cost is unable to be effectively lowered since the control box 91 can just control the single one piece of machining equipment.